High temperature cobalt base alloy



United States Patent" HIGH TEMPERATURE COBALT BASE ALLOY Rudolf H. Thielemann, Palo Alto, Calif., assignor to Sierra Metals Corporation, Chicago, 11]., a corporation of Delaware No Drawing. Filed July 28, 1958, Ser. No. 751,162

8 Claims. (Cl. 75-171) This invention relates to a cobalt base metal alloy, which includes alloying metal additives which make the resulting alloy corrosion resistant and of great mechanical work strength at temperatures up to as high as 1800 F.

Important features of the alloy of this invention are that it may be cast, is highly resistant to oxidation and other forms of corrosion at temperatures up to about 1800 F., and possesses great mechanical work strength at temperatures up to between 1500 F. and 1800 F. As a result, this alloy may be used in the manufacture of blades, vanes, and other parts of high temperature gas turbine engines. Other important uses of the alloy of this invention are in the manufacture of exhaust valves and manifolds in internal combustion engines, in heat exchangers, and in linings for retorts and container vessels used in the chemical and metallurgical industries. 7

The prior art nickel and/or cobalt base metal alloys which have been used as blades, vanes, and other parts of high temperature gas turbine engines, have a maximum operating temperature of about 1500 F. For example, a common nickel-cobalt base metal alloy which incorporates molybdenum as a constituent is for all practical purposes non-utilizable as a structural member in a gas turbine engine if the metal temperature is above 1500 F. The oxidation resistance of such an alloy fails above 1500 F.

Since the alloy of this invention used in blades or vanes in a high temperature gas turbine engine is corrosion resistant and has higher tensile strength at markedly higher temperatures than conventional alloys, the gas turbine engine can be operated at such higher temperature. The performance of the gas turbine engine is improved, in that the total thrust is increased and the amount of fuel consumed per pound of thrust is decreased. p a

The metal alloy of this invention is comprised by weight of approximately: 15 to 30 percent of chromium; to-15 percent of tungsten; from 0.5 to 5 percent of columbium; from 0.1 to 1.3 percent of carbon; from 0.01 to 0.2 percent of boron; and the balance, essentially cobalt. r

I have foundthat the strength characteristics of the alloy of this invention are improved by the addition of the boron, as specified, in an amount of from about 0.01,

percent up to about 0.2 percent. The addition of this constituent in the amounts specified improves the high temperature metallurgical stability and the strength characteristics of the alloy of this invention. However, if the boron content exceeds 0.2 percent, then the alloy of this invention may be unsatisfactory, particularly in those applications where thermal shock requirements are important.

Tantalum may be present in an amount such that if the amount of columbium in the alloy is greater than 3 percent, the combined amount of tantalum and columbium is less than or'equalto 20 percent of the alloy, and if the amount of columbium in the alloy is equal to or less than 3 percent, then the tantalum should never exceed twice the amount of columbium in the alloy.

Molybdenum may be tolerated in the alloy of this While silicon, nickel and iron are not essential ingredients to the metal alloy of the present invention, it has been found that the'addition of small percentages of any one or more of these ingredients, that is, up to about 1.5 percent of silicon, and up to about 5 percent of nickel and/or iron may in certain cases somewhat improve the oxidation resistance of the alloy.

An alloy having the above composition is particularly resistant to oxidation and has high strength at elevated temperatures above 1500 15., so as to be suitable for use in forming cast liners for retorts and container vessels used in the chemical and metallurgical industries as well as for blades or vanes in high temperature gas turbine engines.

To achieve the optimum desired properties, it is preferred that the following impurities in the alloy be held to the following limits by weight. The manganese content in the final alloy should be no more than about 2 percent. The interstitial elements such as nitrogen, hydrogen, tin, lead and the like should be kept as low as possible. In addition, no more than about 0.5 percent total of deoxidizers such as calcium, magnesium and the like should be present.

Following are examples of the preparation and test results of the cobalt base metal alloy of this invention.

Example 1 V A 5 pound alloy melt of a cobalt base metal alloy composition containing about 20 percent of chromium, about 10 percent of tungsten, about 71.4 percent of columbium,

about 0.01 percent of boron, about 0.55 percent of carbon, and the balance, substantially all cobalt, all by melted alloy heat by the usual investment casting tech- 7 nigue under high vacuum conditions. These bars fwere each 3 inches long and inch in diameten The test bars had an elongation of about 5;5 percent i m mft e eeriease. sires. t-l q excess of l00'hours under'a loadlof 25 ,000 pLsIifat'atemperature of 1600 F. in airfand a rupture life in' excess of hours under. aload of 20,000 psi. at a temperature of 1700 F. in air. 1

t H E amp f Q r A. '5 pound alloy 0.01 percent] of boron, aboutg0.5 percent of carbon, and.

the balance, essentially cobalt all by weight, were: piepared in vthesame manner as set forth, in Example '1';

temperature of about 1600 'F.fin,air; and rupture-lite j Patented Mar. 7,

melt and test bars of the same Iii-1 mensions'as set forth in Example 1 of a cobalt ;.-base:' metal alloy composition containing about .ZOpercentdf; chromium,:about l0'percent of tungsten, about l percent of tantalum, about; percentof columbium,::aboutj 3 in excess of 100 hours under a load of 15,000 p.s.i. at a temperature of about 1700 F. in air.

Example 3 A pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containing about 20 percent of chromium, about 7.5 percent of tungsten, about 2.5 percent of tantalum, about 1.5 percent of columbium, about 0.01 percent of boron, about 0.5 percent of carbon, and the balance, essentially cobalt, all by weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 12 percent at room temperature under a tensile stress of 100,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hours under a load of 20,000 p.s.i. at a temperature of about 1600 F. in air; and a rupture life in excess of 100 hours under a load of 15,000 p.s.i. at a temperature of about 1700" F. in air.

Example 4 A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containing about 20 percent of chromium, about 7.5 percent of tungsten, about 2.5 percent of tantalum, about 2.0 percent of columbium, about 0.01 percent of boron, about 0.5 percent of carbon and the balance, essentially cobalt, all by weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 6 percent at room temperature under a tensile stress of 88,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hours under a load of 20,000 p.s.i. at a temperature of about 1600 F. in air; and a rupture life in excess of 100 hours under a load of 15,000 p.s.i. at a temperature of about 1700 F. in air.

Example 5 A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containing about 20 percent of chromium, about 10 percent of tungsten, about 2 percent of tantalum, about 5 percent of columbium, about 0.01 percent of boron, about 1 percent of carbon and the balance, essentially cobalt, all by weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 1 percent at room temperature under a tensile stress of 105,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hours under a load of 20,000 p.s.i. at a temperature of about 1600 F. in air; and a rupture life in excess of 100 hours under a load of 15,000 p.s.i. at a temperature of about 1700 F. in air.

Example 6 A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containing about percent of chromium, about 5 percent of tungsten, about 9 percent of tantalum, about 4 percent of columbium, about 0.01 percent of boron, about 0.65 percent of carbon and the balance, essentially cobalt, all by weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 4 percent at room temperature under a tensile stress of 115,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hours under a load of 20,000 p.s.i. at a temperature of about 1600 F. in air; and a rupture life in excess of 100 hours under a load of 15,000 p.s.i. at a temperature of about 1700 F. in air.

4 Example 7 A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containing about 28 percent of chromium, about 5 percent of tungsten, about 4 percent of tantalum, about 4 percent of columbium, about 0.1 percent of boron, about 0.7 percent of carbon and the balance, essentially cobalt, all by weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of about 7 percent at room temperature under a tensile stress of 110,000 p.s.i.

The test bars of this example had a rupture life in excess of hours under a load of 20,000 p.s.i. at a temperature of about 1600 F. in air; and a rupture life in excess of 100 hours under a load of 15,000 p.s.i. at a temperature of about 1700 F. in air.

Example 8 A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containing about 20 percent of chromium, about 11 percent of tungsten, about 0.5 percent of tantalum, about 1 percent of columbium, about 0.2 percent of boron, about 0.4 percent of carbon, and the balance, essentially cobalt, all by weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 6.5 percent at room temperature under a tensile stress of 100,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hours under a load of 20,000 p.s.i. at a temperature of about 1600" F. in air; and a rupture life in excess of 100 hours under a load of 15,000 p.s.i. at a temperature of about 1700 F. in air.

Example 9 A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containing about 30 percent of chromium, about 5 percent of tungsten, about 3 percent of tantalum, about 2 percent of columbium, about 0.01 percent of boron, about 0.3 percent of carbon and the balance, essentially cobalt, all by Weight were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 5 percent at room temperature under a tensile stress of 90,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hours under a load of 15,000 p.s.i. at a temperature of about 1600 F. in air; and a rupture life in excess of 100 hours under a load of 10,000 p.s.i. at a temperature of about 1700 F. in air.

Example 10 A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containing about 30 percent of chromium, about 5 percent of tungsten, about 3 percent of tantalum, about 2 percent of columbium, about 0.01 percent of boron, about 0.1 percent of carbon, and the balance, essentially cobalt, all by weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 10 percent at room temperature under a tensile stress of 85,00 p.s.i.

The test bars of this example had a rupture life in excess of 100 hours under a load of 15,000 p.s.i. at a temperature of about 1600 F. in air and a rupture life in excess of 100 hours under a load of 10,000 p.s.i. at a temperature of about 1700 F. in air.

Example 11 A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base 5. metal alloy composition containing about 23 percent of chromium, about 7 percent of tungsten, about percent of tantalum, about 5 percent of columbium, about 0.01

percent of boron, about 1.3 percent of carbon, and the balance, essentially cobalt, all by weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 2 percent at room temperature under a tensile stress of 115,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hours under a load of 20,000 p.s.i. at a temperature of about 1600 F. in air and a rupture life in excess of 100 hours under a load of 15,000 p.s.i. at a temperature of about 1700 F. in air.

Example 12 A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containing about 30 percent of chromium, about 5 percent of tungsten, about 5 percent of tantalum, about 3 percent of columbium, about 2.5 percent of molybdenum, about 0.01 percent of boron, about 0.3 percent of carbon, and the balance, essentially cobalt, all by weight, were prapared in the same manner as set forth in Example 1. I

The test bars of this example had an elongation of about 8.5 percent at room temperature under a tensile stress of 100,000 p.s.i. v

The test bars of this example had a rupture life in excess of 100 hours under a load of 18,000 p.s.i. at a temperature of about 1600 F. in air, and a rupture life in excess of 100 hours under a load of 12,000 p.s.i. at a temperature of about 1700 F. in air.

Example 13 A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containing about 18 percent of chromium, about 8.6 percent of tungsten, about 3.5 percent of tantalum, about 3.5 percent of columbium, about 3.5 percent of molybdenum, about 0.1 percent of boron, about 0.5 percent of carbon, and the balance, essentially cobalt, all by weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 4 percent at room temperature under a tensile stress of 100,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hours under a load of'20,000 p.s.i. at a temperature of about 1600" F. in air and a rupture life in excess of 100 hours under a load of 15,000 p.s.i. at a.

temperature of about 1700" F. in air.

Example 14 I A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containingabout 23 percent of chromium, about 5 percent of tungsten, about 5 percent of tantalum, about 3 percent of columbium, about 2.5 percent of molybdenum, about 0.01 percent of boron, about 0.3 percent of carbon, about 1.5 percent of silicon, about 2.5 percent of nickel, about 2.5 percent of iron, and the balance, essentially cobalt, all by weight, were prepared in the same manner as set forth in Ex ample l.

The test bars of this example had an elongation of about 2 percent at room temperature under a tensile stress of 95,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hours under a load of 20,000 p.s.i. at a temperature of about 1600 F. in air and a rupture life in excess of 100 hours under a load of 15,000 p.s.i. at a temperature of about 1700 F. in air.

Example 15 A 5 pound alloy melt and test bars of the samedimensions as set-forth in'Example. 1 of acobalt base. metal alloy composition containing about 20 percent of v chromium, about 10 percent of tungsten, about 1.4 per cent of columbium, about 0.01 percent of boron,' about 0.55 percent of carbon, about 0.2 percent of silicon, about 7 1.0 percent of nickel, about 1.0 percent of iron, and the balance, essentially cobalt, all by weight, were prepared in the same manner as set forth in Example 1.1

The test bars of this example had an elongation of about 6 percent at room temperature under atensile stress of 110,000 p.s.i.

The test bars of this example had a rupture life in V excess of hours under a load of 20,000 p.s.i. at a temperature of about 1600 F. in air, and a rupture life i in excess of 100 hours under a load of 15,000 p.s.i. at a temperature of about 1700 F. in air.

Example 16 A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containing about 20 percent of chromium, about 7.5 percent of tungsten, about 2.5 percent of tantalum, about 2.0 percent of columbium, about 0.01 percent of boron, about 0.5 percent of carbon, about 0.1 percent of silicon, about 1.5 percent of nickel, about 1.5 percent of iron, and the balance, essentially cobalt, all by weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of about 4 percent at room temperature under a tensile stress of 100,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hours under a load of 20,000 p.s.i. at a temperature of about 1600 F. in air and a rupture life in excess of 100 hours under a load of 15,000 p.s.i. at'a temperature of about 1700 F. in air.

Example 17 A 5 pound alloy melt and test bars of the same dimensions as set forth in Example 1 of a cobalt base metal alloy composition containing about 15 percent of chro mium, about 15 percent of tungsten, about 2 percent of a 1" tantalum, about 2.5 percent of columbium, about 0.01 percent of boron, about 0.65- percent of carbon, about 0.1 percent of silicon, about 0.5 percent of nickel, about 0.5 percent of iron, and the balance, essentially cobalt, all by weight, were prepared in the same manner as" i set forth in Example 1.

The test bars of this example had an elongation of aboutS percent at room temperature under a tensile stress of 110,000 p.s.i.

The test bars of this example had a rupture life 'in' excess of 100 hours under a load of 20,000 p.s.i. at a temperature of about 1600 F. in air, and a rupture'life in excess of 100 hours under a load of 15,000 p.s.i. at r 7 a temperature of about 1700 F. in air.

The above detailed description of this inventionihas been given for clarity of understanding only. No un- I necessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art. 7 i i This application is a continuation-in-part of my copending United States application, Serial No. 683,457, filed September 12, 1957, now abandoned. a i 7 Iclaimz' if 1. A metal alloy consisting essentially of by weight? from about 15 to about 30 percent of chromium; fromabout 5 to about 15 percent of tungsten; from about, 0.01 to about 0.2 percent of boron; from about0.5 to? about 5 percent of columbium; from about 0.1 to about 1.3 percent of carbon; and the balance cobalt. I v

2. A metal alloy consisting essentially'of by weight from about 15 to about 30 percent of chromium; from; about 5 to about 15 percent of tungstenyfrom about 0.5 to about 5 percent of columbium; tantalum inanamount. such that if the amount of columbiurn in the alloy 7 more than about 3 percent, the combined amount of tantalum and columbium is less than or equal to 20 percent of the alloy, and if the amount of columbium in the alloy is equal to or less than about 3 percent, the amount of tantalum being never more than about twice the amount of columbium in the alloy; from about 0.01 to about 0.2 percent of boron; from about 0.1 to about 1.3 percent of carbon, and the balance cobalt.

3. A metal alloy consisting essentially of by Weight: from about 15 to about 30 percent of chromium; from about 5 to about 15 percent of tungsten; from about 0.5 to about 5 percent of columbium; up to about 3.5 percent of molybdenum, but not more than about 50 percent of the tungsten present in the alloy; from about 0.01 to about 0.2 percent of boron; from about 0.1 to about 1.3 percent of carbon; and the balance cobalt.

4. A metal alloy consisting essentially of by weight: from about 15 to about 30 percent of chromium; from about 5 to about 15 percent of tungsten; from about 0.5 to about 5 percent of columbium; tantalum in an amount such that if the amount of columbium in the alloy is more than about 3 percent, the combined amount of tantalum and columbium in the alloy is less than or equal to 20 percent of the alloy; and if the amount of columbium in the alloy is equal to or less than about 3 percent, the amount of tantalum being never more than about twice the amount of columbium in the alloy; up to about 3.5 percent of molybdenum, but not more than about 50 percent of the tungsten present in the alloy; from about 0.01 to about 0.2 percent of boron; from about 0.1 to about 1.3 percent of carbon; and the balance cobalt.

5. A metal alloy consisting essentially of by weight: from about 15 to about 30 percent of chromium; from about 5 to about 15 percent of tungsten; from about 0.01 to about 0.2 percent of boron; from about 0.5 to about 5 percent of columbium; from about 0.1 to about 1.3 percent of carbon; up to about 1.5 percent of silicon; up to about 5 percent of nickel; up to about 5 percent of iron; and the balance cobalt.

6. A metal alloy consisting essentially of by weight: from about 15 to about 30 percent of chromium; from about 5 to about 15 percent of tungsten; from about 0.5 to about 5 percent of columbium; tantalum in an amount such that if the amount of columbium in the alloy is more than about 3 percent, the combined amount of tantalum and columbium in the alloy is less than or equal to 20 percent of the alloy, and if the amount of columbium in the alloy is equal to or less than about 3 percent, the amount of tantalum being never more than about twice the amount of columbium in the alloy; up

to about 1.5 percent of silicon; up to about 5 percent of nickel; up to about 5 percent of iron; from about 0.01 to about 0.2 percent of boron; from about 0.1 to about 1.3 percent of carbon; and the balance cobalt.

7. A metal alloy consisting essentially of by weight: from about 15 to about 30 percent of chromium; from about 5 to about 15 percent of tungsten; from about 0.5 to about 5 percent of columbium; up to about 3.5 percent of molybdenum, but not more than about percent of the tungsten present in the alloy; up to about 1.5 percent of silicon; up to about 5 percent of nickel; up to about 5 percent of iron; from about 0.01 to about 0.2 percent of boron; from about 0.1 to about 1.3 percent of carbon; and the balance cobalt.

8. A metal alloy consisting essentially of by weight: from about 15 to about 30 percent of chromium; from about 5 to about 15 percent of tungsten; from about 0.5 to about 5 percent of columbium; tantalum in an amount such that if the amount of columbium in the alloy is more than about 3 percent, the combined amount of tantalum and columbium in the alloy is less than or equal to 20 percent of the alloy, and if the amount of columbium in the alloy is equal to or less than about 3 percent, the amount of tantalum being never more than about twice the amount of columbium in the alloy; up to about 3.5 percent of molybdeum, but not more than about 50 percent of the tungsten present in the alloy; up to about 1.5 percent of silicon; up to about 5 percent of nickel; up to about 5 percent of iron; from about 0.01 to about 0.2 percent of boron; from about 0.1 to about 1.3 percent of carbon; and the balance cobalt.

References Cited in the file of this patent UNITED STATES PATENTS 2,247,643 Rohn et al. July 1, 1941 2,486,576 Savage Nov. 1, 1949 2,515,774 Johnson July 18, 1950 2,684,299 Binder July 20, 1954 2,771,360 Malcolm Nov. 20, 1956 2,855,295 Hansel Oct. 7, 1958 FOREIGN PATENTS 443,821 Great Britain Mar. 6, 1936 686,180 Great Britain Jan. 21, 1953 542,813 Canada June 25, 1957 OTHER REFERENCES Materials and Methods, September 1953, Number 260, page 139.

UNITED CERTIFICATI STATES FATE-N ON OF CORRECTION Patent No.

Thielemann are in the above numbered pat- Letters Patent should read as Rudolf H.

It is hereby certified that error appe ent requiring correction and that the said corrected below.

In the grant,

Signed and sealed this 25th da column 4, line name of inve column 5,

Thielemahn 85,006 p.s.i.

line 1,

udoli H. read d" read w prepared y of July,l961.

(SEAL) Attest: ERNEST W. SWIDER DAVID L. LADD ioner of Patents Attesting Officer Commiss 

1. A METAL ALLOY CONSISTING ESSENTIALLY OF BY WEIGHT: FROM ABOUT 15 TO ABOUT 30 PERCENT OF CHROMIUM, FROM ABOUT 5 TO ABOUT 15 PERCENT OF TUNGSTEN, FROM ABOUT 0.01 TO ABOUT 0.2 PERCENT OF BORON, FROM ABOUT 0.5 TO ABOUT 5 PERCENT OF COLUMBIUM, FROM ABOUT 0.1 TO ABOUT 1.3 PERCENT OF CARBON, AND THE BALANCE COBALT. 